Dual y-axis for different scales in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a dual y-axis plot in matplotlib?

A dual y-axis plot shows two different y-axes on the same graph, each with its own scale. This helps compare two datasets with different units or ranges on one plot.

beginner

Which matplotlib function creates a second y-axis sharing the same x-axis?

The twinx() function creates a second y-axis on the right side of the plot that shares the same x-axis as the original plot.

beginner

Why use different colors for lines and y-axis labels in a dual y-axis plot?

Using different colors helps clearly link each line to its corresponding y-axis, making the plot easier to read and understand.

beginner

How do you label the second y-axis in matplotlib?

After creating the second y-axis with twinx(), use ax2.set_ylabel('label') to add a label to the right y-axis.

beginner

What is a common use case for dual y-axis plots?

They are useful when comparing two related datasets with different units or scales, like temperature and rainfall over time.

Which matplotlib method creates a second y-axis sharing the same x-axis?

A plot()

B twiny()

C twinx()

D subplot()

The twinx() method creates a second y-axis on the right side sharing the x-axis.

Why use a dual y-axis plot?

A To compare two datasets with different y-axis scales

B To plot two datasets with the same scale

C To create a 3D plot

D To plot histograms

Dual y-axis plots help compare datasets with different units or scales on the same x-axis.

How do you label the second y-axis in matplotlib?

A ax.set_xlabel()

B ax.set_ylabel()

C plt.ylabel()

D ax2.set_ylabel()

After creating the second y-axis with twinx(), use ax2.set_ylabel() to label it.

What is a good practice to distinguish lines in a dual y-axis plot?

A Use different colors for lines and y-axis labels

B Use dashed lines only

C Use the same color for both lines

D Use no labels

Different colors help link each line to its y-axis, improving readability.

Which side of the plot does the second y-axis appear by default?

A Left

B Right

C Top

D Bottom

The second y-axis created by twinx() appears on the right side.

Explain how to create a dual y-axis plot in matplotlib and why it is useful.

Think about plotting two lines with different units on one graph.

Describe best practices for making dual y-axis plots easy to read.

Consider how to help the viewer quickly understand which line belongs to which axis.